Sanshools are a main ingredient of a crude drug, “Zanthoxylum Fruit”. In recent years, gamma-sanshool has been reported to have effects such as the activation of TRPV1 and is now in the spotlight of the medicinal chemical field.
The sanshools including gamma-sanshool and delta-sanshool have an unstable structure due to a triene moiety. Therefore, it has been difficult to constantly produce and supply sanshool as a pure substance. Conventionally, from an extract of sanshool as a raw material, sanshool has been isolated and purified by silica gel and ODS column chromatography.
Total syntheses of gamma-sanshool and delta-sanshool have not been reported in the past, but a total synthesis of alpha-sanshool as an analogue of the sanshools has been reported (see Non-Patent Documents 1 and 2). Methods described in the Non-Patent Documents 1 and 2 are both those for forming a triene moiety by a Wittig reaction.